Boring tool

ABSTRACT

Boring tool comprising a wheel in the form of a disk, formed by a substantially circular metal support provided at its periphery with elements made of a hard substance, said elements being plates arranged in a substantially contiguous configuration, the plane of said plates coinciding substantially with the plane of symmetry of said wheel perpendicular to the axis of rotation so as to produce a continuous crown.

United States Patent [191 Metge BORING TOOL [75] Inventor: Emile Metge,Paris, France [73] Assignee: Union Industrielle Blanzy-Quest,

Paris, France [22] Filed: Nov. 2, 1972 [21] App1.No.:303,155

[30] Foreign Application Priority Data Nov. 10, 1971 France "7140324[52] US. Cl. 175/373, 175/374 [51] Int. Cl. E2lc 13/01 [58] Field ofSearch 175/327, 351, 371375, 175/410 56] References Cited UNITED STATESPATENTS 1,516,340 11/1924 Holdaway et al. 175/351 1,691,623 11/1928Black 175/373 X Feb. 12, 1974 2,121,202 6/1938 Killgore 175/3742,223,864 12/1940 Zublin 175/373 2,887,302 5/1959 Gar'ner 175/3743,191,699 6/1965 Robbins et al.. 175/374 3,596,724 8/1971 Bechem l175/375 3,679,009 7/1972 Goodfellow l t 175/372 X Primary Examiner-DavidH. Brown Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn &Macpeak [57] ABSTRACT Boring tool comprising a wheel in the form of adisk, formed by a substantially circular metal support provided at itsperiphery with elements made of a hard substance, said elements beingplates arranged in a substantially contiguous configuration, the planeof said plates coinciding substantially with the plane of symmetry ofsaid wheel perpendicular to the axis of rotation so as to produce acontinuous crown.

7 Claims, 6 Drawing Figures PATENTERF'EB T 2 RM SHEET 1 RT 2 FIG. 1PRloR ART) FIG. 2(PRIOR ART) F IG. 3(PRT0R ART) PAIENI FEB 1 21914 SHEET2 BF 2 FIGS lllll Ill.

FIG.6

BORING TOOL BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention concerns a boring tool, more particularly for acontinuous boring machine and for hard ground, and relates, moreparticularly, to a tool comprising a wheel in disc form consisting of asubstantially circular metal support provided at the periphery withelements made of a hard substance.

-2. Description of the Prior Art It is known, indeed, that when theground reaches a certain threshold of hardness, many manufacturers equiptheir boring machines with tools provided with tungsten carbide studs.These studs are generally arranged on a substantially circular metalsupport of the boring disk type in a same plane, or possibly in twoneighboring parallel planes, perpendicular to the axis of the saidsupport and with a relatively great peripheral interval, while the studsare cylindrical with spherical ends.

The shape of the studs and their arrangement on their metal supportresult in essentially discontinuous stresses on'the support of the wheelwhen the latter rotates freely about its axis, rolls on the groundduring boring, giving rise to vibrations in the link members, moreparticularly in the case of sweeping arm machines, and reducing theirservice life.

In FIGS. 1 and 2, the prior art studded tungsten carbide wheel forboring in hard ground has an outer diameter comprised of between 300 and400 millimeters, whereas the peripheral spacing P is in the order of 40millimeters. The studs 1 are cylindrical and have spherical outer ends,their diameter being in the order of 15 millimeters, and they are fittedin a metal support 2 by embedding.

In FIG. 3, the curve 3 represents the variation of the stress F to whichthe wheel 2 is subjected during the course of time t.

It will be seen thatthe duration A of the active phase, that is, thephase during which a stud digs into the rock, andis subjected to amaximum stress M, is short in relation to the time B which passesbetween the successive digging actions of two neighboring studs. Thattime B is in the order of a hundredth of a second, whereas A is aboutfive times less. I

It will also be noted that between two active phases, the normal stressbecomes negative and has a minimum m, due to the resilient nature of thewheel and of its support, and assumes only small positive values m.

The result of this is that violent shocks occurring during the activephases expose all the mechanical elements linked to the wheel to highperiodic alternate stresses. I

These various mechanical elements are inevitably assembled together witha certain amount of play, or by slightly rigid linking means. Primaryshocks due to boring during the active phases induce, at the level ofthese linking means, secondary shocks in which the energy of the primaryshocks is dissipated.

Practically, these phenomena result in wear, damage or breakage of thelinking means, more particularly of the bearings, bushings, bolts andscrew threads.

The direct disadvantages of this type of wheel are:

On the one hand,'adanger of breakage of the studs,

I on the other hand, the short service life of the metal support, onwhich the wear between thestuds by abrasion causes the baring of thestuds, thus resulting in their breakage by bending.

It is therefore important to find means for limiting or even removingthese causes of damage, and this is the aim of the present invention.For that purpose, the continuity of the cutting edge of the wheel, thatis, of the hard parts of the latter in contact with the cutting face andpenetrating the rock to bore it away, is reestablished.

SUMMARY OF THE INVENTION The essential feature of the invention consistsin the use of plates made of ahard substance arranged in a substantiallycontiguous configuration, the plane of said plates coincidingsubstantially with the plane of symmetry of the wheel, perpendicular tothe axis of rotation, so as to produce a continuous crown.

The aims and advantages of the present invention will become apparentfrom the following description of an embodiment related to the.drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 show a known wheelfitted with studs,

respectively in an elevation view and in a transversal cross-sectionview.

FIG. 3 shows variations, in the course of time, of the stress applied tothe wheel in FIG. 1.

FIGS. 4 and 5 show a wheel according to the invention, illustratedrespectively in an elevation view and in a transversal cross-sectionview.

FIG. 6 shows the variations in the force applied, in the course of time,to the .wheel in FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIGS. 4 and 5, the wheelaccording to the invention comprises the metal support 5 in the shape ofa biconical circular ring, made of steel which resists abrasion, whiletungsten carbide plates 4, arranged contiguously or at a slight distancefrom one another, so that the unit forms a continuous crown, are fixedby brazing in a circular groove formed in the said ring.

The embedded portion of the tungstencarbide plates 4 in the metalsupport 5 is greatly increased in relation to that of the cylindricalstuds 1 in FIG. 1 that danger of breakage by bending is hence greatlyreduced.

Moreover, in a conventional wheel, wear by abrasion between the studs isoften very fast, especially when the ground contains silica; thisresults in baring of the studs which rapidly causes their breakage bybending. Nothing of the sort can occur in the case of contiguous plates.Wear by abrasion concerns only the lateral faces of the metal supportand is consequently very much slower because of the slight pressure towhich they are subjected, and the service life of the tool is henceconsiderably lengthened.

The cumulated stoppage time of a boring machine resulting from theadding of the durations of each change of wheels is thus appreciablyreduced because stoppage periods are rare, and this directly causes asubstantial improvement of the overall efficiency of the said machine.

The retaining of the plates 4 in their embedding recesses is insured byany known means, more particularly by brazing on the support 5 accordingto any current technique, normally in a neutral atmosphere or in avacuum; the support being adapted to facilitate the operation, or evenby crimping.

In FIG 6, the curve 7 represents the speed of the variations in thetotal stress F applied, during the course of time t, on the wheel ofFIG. 4 for which a number of plates equal to 20, that is, equal to thatof the studs in FIG. 2, has been chosen.

Nevertheless, it is observed that the normal stress between twoconsecutive active phases is no longer cancelled as in a conventionalstudded wheel, as stated in FIG. 3, but keeps a relatively high positivevalue M. That positive value represents, at the level of the link meansbetween the mechanical elements linked to the wheel, pre-stress effortswhich take up any possible play and increase the rigidity of the linkmeans.

These pre-stress efforts make it possible to transmit the energy due toprimary shocks across the mechanical elements linked to the wheelwithout any secondary shocks occurring at the level of the link means.Downstream from the above-mentioned mechanical elements, the energy ofthe primary shocks is either retransmitted to the ground, or absorbed bya suitable damping element. Damage to the connection elements isprevented or at least greatly reduced.

It must be understood that the description set forth above of anembodiment of the invention constitutes only an example having nolimiting character, and that numerous variations which will be obviousto the man in the art and correspond to the general definition which hasbeen given thereof, do not go beyond the scope of the protection appliedfor.

Thus, inasmuch as concerns the plates, any substance having a hardnesswhich is at least equivalent to that of tungsten carbide, either in thecarbide family or in the nitride family, or even ceramic plates of thetype used for machining tools and known under the trade name ofceroxydes, may furthermore be used.

It is known that the hardness qualities of a substance increase in thesame direction as the fragility; that is why the plates whose greatestsurfaces are arranged parallel to the transversal plane of symmetry ofthe support are embedded between two lateral cheeks insuring therequired mechanical properties thereof.

What is claimed is:

1. In a boring tool comprising: a wheel in disk form consisting of asubstantially circular metal support provided at the periphery withelements made of a hard substance, the improvement wherein: saidelements comprise plates arranged in a substantially contiguousconfiguration with the plane of the said plates coinciding substantiallywith the plane of symmetry of the said wheel perpendicular to the axisof rotation, so asto form a continuous crown. V

2. The boring tool according to claim 1, wherein: said plates are fixedin a circular groove arranged in the plane of symmetry of the support,and wherein the support has the shape of a biconical circular ring.

3. The boring tool according to claim 1, wherein: the plates are made ofone material of the group consisting of carbides and nitrides.

4. The boring tool according to claim 1, wherein the plates are made ofa ceramic substance.

5. The boring tool according to claim 1 wherein: the plates are fixed tothe support by brazing.

6. The boring tool according to claim 2 wherein: the plates are fixed tothe support by brazing.

7. The boring tool according to claim 3, wherein: the

plates are fixed to the support by brazing.

1. In a boring tool comprising: a wheel in disk form consisting of asubstantially circular metal support provided at the periphery withelements made of a hard substance, the improvement wherein: saidelements comprise plates arranged in a substantially contiguousconfiguration with the plane of the said plates coinciding substantiallywith the plane of symmetry of the said wheel perpendicular to the axisof rotation, so as to form a continuous crown.
 2. The boring toolaccording to claim 1, wherein: said plates are fixed in a circulargroove arranged in the plane of symmetry of the support, and wherein thesupport has the shape of a biconical circular ring.
 3. The boring toolaccording to claim 1, wherein: the plates are made of one material ofthe group consisting of carbides and nitrides.
 4. The boring toolaccording to claim 1, wherein the plates are made of a ceramicsubstance.
 5. The boring tool according to claim 1 wherein: the platesare fixed to the support by brazing.
 6. The boring tool according toclaim 2 wherein: the plates are fixed to the support by brazing.
 7. Theboring tool according to claim 3, wherein: the plates are fixed to thesupport by brazing.